MSL Chemistry and Mineralogy X-ray Diffraction X-ray Fluorescence (CheMin) Instrument

Wayne Zimmerman wayne.f.zimmerman@jpl..gov Dr. Dave Blake Blake, David F (6700-NASA) William Harris [email protected] John Michael Morookian [email protected] Dave Randall [email protected] Leonard J. Reder [email protected] Dr. Phillipe Sarrazin [email protected] Jet Propulsion Laboratory California Institute of Technology 4800 Oak Grove Drive M/S 306-416 Pasadena, CA 91109-8099 818-354-0234

Abstract—This paper provides an overview of the Science Laboratory (MSL) Chemistry and Mineralogy X- 1. MISSION OVERVIEW ray Diffraction (XRD), X–ray Fluorescence (XRF) (CheMin) Instrument, an element of the landed Launched in the fall of 2011, the Mars Science rover payload, which landed on Mars in August of 2012. Laboratory (MSL) is part of NASA's Mars Exploration The scientific goal of the MSL mission is to explore and Program, a long-term effort of robotic exploration of the quantitatively assess regions in Crater as a potential red planet. is a rover that will habitat for life – past or present. The CheMin instrument assess whether Mars ever was, or is still today, an will receive rock and soil samples from the MSL environment able to support microbial life. In other Sample Acquisition/Sample Processing and Handling words, its mission is to determine the planet's (SA/SPaH) system, and process it utilizing X-Ray spectroscopy methods to determine mineral composition. "habitability." MSL mission high- lights are summarized The Chemin instrument will analyze and rocks in Table 1 and MSL CheMin instrument highlights are to enable scientists to investigate geophysical processes summarized in Table 2 [1]. MSL successfully landed on occurring on Mars. The CheMin science objectives and August 5, 2012 (PDT). proposed surface operations are described along with the CheMin hardware with an emphasis on the system The science objective of MSL is to “explore and engineering challenges associated with developing such a quantitatively assess a local region on the Mars surface as complex instrument. a potential habitat for life, past or present.” The duration of the primary mission of MSL will be 670 sols, or one Table of Contents Mars year. During this time, the rover will traverse to at least three geologically distinct sites within its landing 1. MISSION OVERVIEW ...... 1 ellipse, and determine the “habitability” of these sites. 2. HARDWARE OVERVIEW ...... 3 Habitability is defined in this context as the “capacity of 3. SOFTWARE OVERVIEW ...... 7 the environment to sustain life.” 4. TECHNICAL CHALLENGES ...... 8 5. SUMMARY AND CONCLUSIONS ...... 12 MSL will rely on new technological innovations, REFERENCES ...... 13 especially for landing. The spacecraft will descend on a BIOGRAPHY ...... 14 parachute and then, during the final seconds prior to

Paper 2062, IEEE/AIAA 2013, Revision #10 1 landing, lower the upright rover on a tether to the surface, The rover will analyze dozens of samples scooped from the much like a sky crane. Once on the surface, the rover will soil and drilled from rocks. The record of the planet's be able to roll over obstacles up to 75 centimeters (29 climate and geology is essentially "written in the rocks and inches) high and travel up to 90 meters (295 feet) per soil" – in their formation, structure, and chemical composi- hour. On average, the rover is expected to travel about 30 tion. The rover's onboard laboratory will study rocks, soils, meters (98 feet) per hour, based on power levels, and the local geologic setting in order to detect chemical slippage, steepness of the terrain, visibility, and other building blocks of life (e.g., forms of carbon) on Mars and variables. will assess what the Martian environment was like in the past. The rover carries a radioisotope power system that Table 1: MSL Mission Highlights generates electricity from the heat of plutonium's radioactive decay. This power source gives the mission an Mission Mars Science Laboratory (MSL) operating lifespan on Mars' surface of a full Martian year Life-Cycle Phase Phase C-E (Design/Build/Ops) (687 Earth days) or more, while also providing Mission Type Surface, Rover Instrument significantly greater mobility and operational Competed vs. Directed, Mars Program flexibility, enhanced science payload capability, and Directed exploration of a much larger range of latitudes and Manage, build, launch, operate JPL Role altitudes than was possible on previous missions to high-capability ; Mars. While the MSL rover will carry a variety of in-situ Contractors Lockheed Martin Space Systems: instrumentation for collecting Mars data from the surface, spacecraft Alliance Space Systems this paper focuses primarily on the CheMin Instrument. Inc.: robotic arm Inheritance Viking, Mars Pathfinder, Mars Science Objectives Exploration Rover (MER) DoE (GRC, MSFC) RPS MSL is intended to study Mars’ habitability. It will carry Hardware Spacecraft, sky crane, rover, the biggest, most advanced suite of instruments for instruments scientific studies ever sent to the . Their Science Cameras: purpose is to assess whether Mars ever had an Instruments/ Mast Camera environment capable of supporting microbial life. More Engr. Instruments specifically, MSL has the following science objectives: Mars Descent Imager Spectrometers: Biological objectives: Alpha Particle X-Ray Chemistry o Determine the nature and inventory of organic & Camera Chemistry & carbon compounds Mineralogy o Inventory the chemical building blocks of life X-Ray Diffraction (carbon, hydrogen, nitrogen, oxygen, phosphorous, and sulfur) Instrument Suite o Identify features that may represent the effects of Radiation Detectors: biological processes Radiation Assessment Detector Dynamic Albedo of Neutrons Geological and geochemical objectives: Rover Environmental Monitoring Station o Investigate the chemical, isotopic, and Primary Science Assess the history of environmental mineralogical composition of the Martian surface Objective conditions on Mars at sites that may and near-surface geological materials once have been wet and favorable to o Interpret the processes that have formed and life. modified rocks and soils Cost Total cost $1,700M (estimated) Pre-Phase A start 10/01/2001; Mission Start Planetary process objectives: Phase A start 11/24/2003 o Assess long-timescale (i.e., 4-billion-year) Launch Date November, 2011 atmospheric evolution processes Launch Vehicle 541 o Determine present state, distribution, and cycling Launch Site Cape Canaveral Air Force Stn of water and carbon dioxide Project Manager Peter Theisinger, Deputy PM Richard Cook Surface radiation objective: Project SE Joel Krajewski o Characterize the broad spectrum of surface Flight System SE Ann Devereaux radiation, including galactic cosmic radiation, solar Project Scientists John Grotzinger (Caltech) proton events, and secondary neutrons Ed Stolper (Caltech)

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Science Payload David Blake (ARC) Objective of mineralogical composition of the Principal Ken Edgett (Malin Space CheMin Martian surface and near-surface Investigators (PIs) Science Systems) Instrument geological materials Science Payload Don Hassler (Southwest Development: $39.9M cost CheMin Cost Principal Research Institute) Capped Investigators (PIs) Paul Mahaffy (GSFC) Instrument Start (Con’t.) Michael Malin (Malin Space 2002 Science Systems) Instrument Wayne Zimmerman (Current) Igor Mitrofanov (Space Manager Research Institute) David Blake, PI (ARC) CheMin Luis Vázquez (Center for David Vaniman, Deputy PI Principal Astrobiology, Madrid) Albert Yen, Investigation Roger Wiens (Los Alamos National Investigators Scientist Lab) MSL CheMin http://marsprogram.jpl.nasa.gov/

Website msl/mission/sc_instru_chemin.ht ml Chemin Instrument Science Objectives

2. HARDWARE OVERVIEW The CheMin X-ray Diffraction (XRD) instrument will be principally engaged characterizing the geology and MSL will truly be a chemistry laboratory on wheels. Going geochemistry of the landed region at all appropriate spatial beyond just having a very powerful "fistful" of instruments scales (i.e., ranging from micrometers to meters). The as MER’s Spirit and Opportunity rovers do, MSL will also science objective of the CheMin instrument is to investigate take samples onboard and analyze them. Some instruments the chemical and mineralogical composition of the Martian on MSL inherited significant technology from their surface and near-surface geological materials to provide predecessors on the Mars Exploration Rovers, but they are, scientists the information needed to interpret processes that indeed, "next generation" in terms of capability. have formed and modified rocks and regolith.

CheMin is a definitive mineralogy instrument, meaning that Table 3: Science Investigations for CheMin Instrument the emphasis is on measurements that will aid in MSL Science understanding aqueous processes on Mars. This is an Goals MSL CheMin Measurements essential role within the MSL analytical instrument laboratory. Moreover, Table 3 [2] shows the relationship Identification and quantification of between NASA’s MSL science goals and specific CheMin Mineralogical water-precipitated/deposited minerals characterization by XRD - clays, micas, hydrates, measurements. of hydrous evaporitic mineral suites (sulfates, processes. halides, borates, nitrates, etc.), Table 2: MSL CheMin Instrument Highlights carbonates, silica polymorphs. Chemistry & Mineralogy X-Ray Instrument Identify & Identification and quantification of Diffraction (CheMin) characterize phases carbonates, hydrates, nitrates, containing phosphates, sulfides and sulfates by Phase C-E Design/Build/Ops) Life-Cycle Phase C,H,O,N,P,S XRD. Identification and quantification of Fe, Instrument Type Spectrometer Determine the array Mn,S– containing minerals via XRD, of potential energy elemental analysis of Fe (Iron), Mn CheMin instrument management, sources on Mars (Manganese) and S by XRF.

JPL Role implementation, and operations. Inventory chemical building blocks of Identification and quantification of carbon-containing minerals – X Ray Source – Oxford life, identify carbonates, graphite having a range of Instruments (Lack of JPL Capability) features that may crystallinity, by XRD. Provide record biologically Instrument CCDs – E2V (UK) (Only available mineralogic context for organic relevant processes Contractors source for technology) Coolers – carbon measurements by other RICOR (Lack of JPL Capability, that have taken instruments. Best available supplier) place over time. Mineralogical Mineralogical identification and Inheritance CheMin3 prototype field unit characterization of quantification of carbonates, nitrates, samples containing phosphates, sulfides and sulfates by CheMin C,N,P, or S XRD. Instrument X Ray Source, CCDs, Coolers Interpret the Identification and quantification of Hardware processes that have aqueous and diagenetic minerals in the Primary Science Investigate the chemical and formed and context of their host rocks and facies

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During testing of the CDD installed in the CheMin each analysis frame. Data are stored in non-volatile flash instrument, it was shown that for a temperature range of -10 memory. When the rover 'wakes up', it commands CheMin to -35 °C, reliable XRD data could be acquired with using to transfer the data into RCE memory, thus completing one the CCD which was promising given the capability of the of analysis. cryo-cooler to take the detector to even lower temperatures. CheMin Software Operational Scenario Electronics A normal operational scenario depends heavily on the Rover The CheMin electronics provide signal handling for the Compute Element software. The sequence of events will CCD and digitization of CCD data. There is non-volatile nominally be to turn on CheMin, receive multiple samples storage for several thousand datasets, each nominally from the SA/SPaH system, and dispose of them to clean the representing 30 seconds of analysis. Internal temperature cell, then acquire a final sample for analyses using the sensors and voltage levels are monitored. Science and SA/SPaH system. CheMin is commanded to shake both its engineering data are passed to the Rover via a digital funnel and cell to distribute the sample for analysis. Once interface. In addition, CheMin electronics must provide the sample is in the cell, CheMin operation is suspended interfaces for the cryocooler, x-ray source (XRS), 2 motors until the Martian night when other functionality aboard the used to rotate the sample wheel, a paraffin actuator, and a rover will be disabled. decontamination heater for the CCD. Sample wheel position telemetry must be monitored. Three piezoelectric During the Martian night, the RCE sends commands to the actuators on the funnel and 16 on the sample wheel are instrument to (1) turn it on, (2) cool the CCD detector and individually commandable. Finally, power must be (3) ramp up the high voltage on the X-ray tube. After CCD provided for the electronics, x-ray source (and its heaters), and X-ray source devices are stable, samples are shaken and the cryo-cooler. again. The RCE commands the instrument to start data collection and store results into flash memory within the 3. SOFTWARE OVERVIEW instrument.

CheMin does not have a microprocessor, but has embedded During data collection, successive X-ray exposures are software (firmware) within the instrument FPGA. Control is combined to provide longer integrations of up to 10 hours implemented in a one-time field-programmable gate array needed to meet the science requirements. Large data (FPGA), which contains several distinct processors (state volumes are generated by operating the CCD as a single machines), each responsible for its own element. Processes photon counting device. CheMin stores all of the communicate via discrete semaphores (flip flops), and are uncompressed data prior to transmission to the rover. controlled by uploadable parameters. A single command can initiate a complex process involving many of the Housekeeping data is also generated at a rate equal to the CheMin elements in a sequence that can last many hours. rate at which exposures are taken, nominally every 30 This allows CheMin to operate autonomously during the seconds, even when X-ray analysis is not happening. Martian night, having no interaction with the Rover once Housekeeping data consists of internal temperature and commanded. voltage readings of various components within the instrument. There is sufficient flash (non-volatile) memory At the beginning of the Martian night, the RCE sends to store all of the raw data and housekeeping data for an commands to the instrument to turn it on and to analyze the entire analysis, with margin. sample. The Rover then begins its nightly hibernation. CheMin verifies that temperatures are OK for analysis, The data collection and storage are done autonomously ramps up the high voltage on the x-ray source, and enables within the instrument. Data processing and transmission to the cryocooler. When the XRS is ready, and the analysis Earth is done by the RCE. On completion of an analysis temperature has been reached, CheMin begins vibrating the session, the RCE will turn off the instrument. piezo on the cell under analysis and begins saving frames of data. Periodically, the cell piezo changes from normal CheMin data will be provided through the MSL Ground vibration mode to a so-called 'chaos' mode for one frame, to Data System (GDS), however, CheMin will have its own further agitate the sample. Earth scientists do this 'by hand' GDS. The CheMin GDS will be designed to provide the while analyzing on earth, so CheMin was designed to mimic requisite technical science and engineering products from this. Since this entire operation is autonomous, CheMin the instrument. also maintains a robust set of parameters and conditions that 4. TECHNICAL CHALLENGES will cause it to safe if violated. Under normal operation, when the requisite number of data frames have been The technical challenges of developing a CheMin acquired, CheMin ceases data collection, ramps down the instrument actually started long before the MSL mission XRS, takes one frame of dark data, and shuts everything off. concept was finalized, with the development of field CheMin waits in idle mode until morning. All housekeeping instruments. The history of how these field instruments telemetry, parameters, and machine state are saved with evolved into flight instruments is described below. 7

Challenges encountered during development of CheMin CheMin Project negotiated with MSL to increase the included meeting requirements for weight, volume, power, original 5 Kg allotted weight to the current 12.4 Kg. and thermal properties. Additional challenges involved uncovering late signal noise issues, flying a unique sample CheMin flight volume has remained stable and fits nicely handling system, and the problems associated with the into the allocated volume of 30 cm. x 29 cm. x 27 cm. This development of an X-ray source for flight. Lastly, there was was achieved by careful tradeoff analysis. Early on, it was the challenge of developing the FPGA firmware on planned that the instrument would contain two X-ray schedule. sources (XRS), but it was discovered that two XRS would not fit into the limited volume available. A decision was Technology Readiness Level made to eliminate one XRS. Originally, the intention was to do true quantitative XRF with one XRS. XRD would be Mineral analysis using the XRD/XRF technique in the done using the other XRS. XRF requires higher energy and laboratory has been performed for some time [4]. It was not less beam collimation precision, while the XRD requires until the early 1990’s that groups began to deploy less energy and a narrow, more precise beam. True instruments to the field to perform in-situ XRD/XRF quantitative XRF requires both a measurement of reflected mineral analysis. These units were initially rather large, and transmitted x-ray energy. This requires an extra X-ray bulky, and power hungry. With advancements in detecting diode to measure reflected X-ray energy. A components, smaller and lower power field instruments, common CCD detector measures the transmitted X-ray generically known as “CheMin”, began to be implemented energy. Problems with procuring a flight qualified diode for around 2001. By 2003, there was an instrument (known as XRF, schedule pressure, and the need to reduce volume CheMin 3) that began to demonstrate the true feasibility of resulted in the instrument team deciding to reduce the XRF future extraterrestrial usage. Figure 7 shows the CheMin 4 to a qualitative measurement utilizing transmitted energy in Death Valley, CA in 2004 [5]. This instrument was only. This decision was determined not to have any implemented as the next step after CheMin 3. The prototype volume requirement for the instrument to be met. instrument, which can be hand-carried to remote locations, weighs about 20 kg. A geologist's hammer is shown for The MSL rover power system provides CheMin with 2 amp scale. and 4 amp switches to supply the instrument with suitable current. The MSL Project keeps an energy budget. The flight energy requirement for CheMin is 750 Watt-hours and the current best estimate of usage is 719 Watt-hours. CheMin is within the MSL energy budget for the instrument with a little margin. However, the power requirement comes from meeting thermal interface requirements that were a challenge for the instrument team.

Thermal Challenges

CheMin was originally designed to operate within a temperature range of -40 °C to +50 °C. As the design matured, X-ray source design limitations limited the thermal operating range to -20 °C to +20 °C. This range is maintained passively by the design of the thermal paths and structure connecting the instrument to the Rover Avionics (Death Valley, CA 2004) Mounting Plate (RAMP), which is temperature controlled. As designed for normal Mars operations, the CCD is cooled Figure 7: CheMin 4 Prototype Instrument to -100 C below the RAMP temperature. However, higher than expected heat leaks to the CCD were caused by three Weight, Volume & Energy Limits primary sources:

The spaceflight CheMin instrument (shown in Figure 1) (1) The thermal model done for the CDR predicted looks much different than the prototype and weighs about approximately a factor of five lower heat flow from the alignment bench to the CCD than estimated in 10 kg [5]. The MSL flight requirement for the instrument is the final thermal model. In a vacuum environment a weight of less than 12.4 Kg. Weight reduction from the the CCD cools to -100oC. However, in the Martian prototype was achieved through a series of careful materials environment (predominately CO2) temperatures are choices and updates to the CheMin mechanical design. limited to -55oC to -60oC below the RAMP However, meeting the weight requirement for CheMin was temperature. This is due to high heat conduction a challenge since during the redesign of the high voltage through the small gaps between parts of the CCD power supply, ruggedization for flight added mass to the light baffle and support which are very close to the instrument. The extra weight could not be eliminated, so the

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bench. The heat leak was increased by the X-Ray Source Challenge 0.0012” thick copper plating under the gold plating on the CCD baffle. Redesign of the The field instrument experience was a catalyst for the choice interface was not feasible. of CCD detector and X-ray source. The E2V Company was used for the CCD detectors because they had lots of (2) The CDR thermal model predicted a lower heat experience, and had flown on previous missions (such as flow through the cryo-cooler bumper tube to the MER). Initially, there was concern about using residual cryo-cooler cold finger by about a factor of six as parts, so the project decided to purchase new devices. This compared to the final thermal model. The worked out well; however, the procurement of the X-ray difference was primarily caused by the source would be more difficult. unaccounted for plating of 0.0012” copper on the inside and outside of the bumper tube. The effect Oxford X-Ray Technology Group, Inc., working with was mitigated by replacing the bumper tube with NASA Ames, developed a small X-Ray tube through a one having no copper plating and covering the NASA SBIR program. The X-Ray tube had been used in inside and outside of the cryo-cooler bumper tube field instruments and seemed like a logical choice. The X- with a layer of gold foil. Ray source procurement was a critical item for CheMin, and because Oxford had experience, the initial decision to (3) The CDR thermal model predicted around a two purchase the X-Ray source (e.g., X-ray tube and high and one-half times lower heat flow through the voltage power supply integrated into a single package) from Titanium CCD support than was estimated in the them made sense. final thermal model. This was caused by a modeling error. Redesign of the interface was not As a result, the company was not well aligned with the feasible due to schedule constraints. delivery of single, highly qualified components, including a detailed paper trail of testing and characterization history. Schedule slip of the Developmental Model (DM), due to They were more aligned toward delivering many budget constraints, eliminated an early thermal test in components for manufacturing a series of commercial X- vacuum which had it been done in a simulated Martian Ray products. Environment, would have flagged this thermal issue. Fortunately the performance of the E2V CCD in terms of Oxford’s inability to supply flight qualified components led low noise/dark current was significantly improved from the the CheMin Project in 2006 to a new strategy for obtaining previous versions allowing satisfactory science return. a flight ready X-ray source assembly. JPL itself would manufacture the assembly and qualify it for flight. The X- There is an operational constraint for the X-ray source at the ray tube would still be purchased from Oxford since this interface to the RAMP of +20 °C. The CCD detector needs device was clearly beyond the Lab’s capability. A set of to be very cold, while the X-ray source operates warm. eight X-ray tubes were purchased. JPL put the tubes Attempting to balance all the thermal requirements is non- through extensive environmental and life testing. There was trivial. The CheMin instrument has heat in all the wrong particular concern about the tungsten filament within these places, so proper temperature ranges on components are tubes passing vibration qualification. After all testing was maintained using active heaters and coolers. Maintaining completed, device characterization and inspection screening proper temperature ranges is a particularly difficult were used to select suitable tubes for flight. A flight tube, engineering challenge. one spare and a development model tube, were finally selected. There are 11 temperature sensors that are read by CheMin. These monitor the X-ray source, CCD detector and various Development of the high voltage power supply (HVPS) was mechanical assembles. The CCD detector and X-ray source assigned to the radar division at JPL. It was a challenge are the most critical components for temperature control. because the HVPS needed to be integrated into a small, The CCD (as discussed above) is conductively cooled by a tightly fitted space with assurance that suitable isolation to Stirling-cycle cryo-cooler connected to the CCD via a protect against arcing would be provided. flexible thermal strap. The X-ray Source dissipates 13 W when operating, to keep temperature from exceeding the To provide electrical insulation, the high voltage power +20 °C limit. Most power is dissipated via conduction supply is filled with a dielectric insulator, a mixture of through a thermal strap and jacket around the high voltage sulfur hexafluoride (SF6) gas and gaseous nitrogen (N2). power supply (HVPS) to an alignment bench with the X-ray The mixing ratio is selected to keep it gaseous over the full tube. To ensure the HVPS package temperature does not operating temperature ranges. The gas mixture was chosen exceed allowable operational limits, a thermal jacket is to be gaseous down to -40°C for protection of the HVPS. mounted on the package with a high conductivity thermal strap connecting it to the alignment bench. The 3 watts The high-voltage power supply and controller interface the produced in the tube are dissipated to the alignment bench main instrument electronics to the X-ray tube. The HVPS via the copper alignment spacer. produces the various voltages required by the tube elements. The HVPS produces the -28 kV cathode voltage, the 9 filament current (nominally 1.3 A), and the focus voltage In order to save schedule, the CheMin DM (demonstration (nominally -90 V, referenced to the cathode voltage). The model) was descoped as a deliverable, and the decision was high-voltage power supply is housed in a laser-welded made to proceed directly with the building and testing of the stainless steel "can" and is integrated directly with the X-ray flight model (FM). While this plan was very successful tube (via a laser welding process). The controller is with regard to the FM delivery, it left CheMin scientists separated from the high-voltage section and is integrated without a means to replicate CheMin performance on the with the support structure used to mount the X-ray Source to Earth. The DM electronics still had to be produced for the alignment bench. All the manufacturing, design and FPGA development and testing, but were done so with no testing of the X-ray source proved to work out well and be regard to replicating FM performance. A program was within the Lab’s capability. undertaken to bring the CheMin DM up to flight-like status.

Signal-to-noise (SNR) and Signal Quality Challenge While the flight unit met the above performance requirement with margin, an issue arose after the flight unit As the CheMin instrument design was evolving a significant was integrated into the rover and launched. The team effort was put into developing a high fidelity performance proceeded with its sample testing/characterization using the and error budget model [6]. As the reader can see from development model (DM) instrument. However, as the Figure 4, there are several variables that effect both the testing proceeded on the DM, it was noted that the returned alignment of the instrument and subsequent beam alignment spectra exhibited noise which masked the actual signal. The error could not exceed 0.35 degrees off center. Considering SNR was not anywhere close to what was observed on the all sources of alignment error, it was determined that indeed flight unit. Since the DM electronics were designed to the mechanical and optics design could maintain that error emulate the flight and now had significant operational hours requirement but not with any significant margin. That said, logged, the poor SNR raised suspicions that perhaps there the subsequent performance model showed that even was the potential for a component failure on the flight unit operating the detector at higher temperatures than desired, which would be mission ending. A Tiger Team was formed the SNR was projected to 2x higher than the requirement. to determine root cause. The team proceeded to develop a Figure 8 shows the modeling results. detailed fault tree and examine every possible noise source.

Figure 8: Results of SNR Model

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Time was of the essence because MSL had already The major challenge faced when deploying the new sample launched, and there was only 5 months before landing. By handling system is to understand the physics of sample probing the boards and examining the output signal, the excitation under Mars environmental conditions and then team isolated the analog, utility, and power boards as the designing a test program for handling and characterizing all likely source for the noise. The team found that a of the possible materials this system could encounter. combination of non-flight parts, significant hay-wiring/poor Examples of the critical variables that had to be understood routing providing sources for stray inductance, and failed are [8]: solder pads were the primary causes for the noise. Ultimately, the decision was made to completely re-build 1. Variable particle sizes which may affect the the analog and utility boards using all qualified flight parts. momentum transfer between particles; The re-built boards were re-integrated with the DM 2. Variable particle geometries which may also effect instrument and re-tested. The DM performance matched the the motion dynamics, and particle-to-particle flight and proved that the flight unit was indeed robust. interactions (e.g., friction), see Figure 10; Figure 9 shows how the SNR changed with the rebuild. 3. Electrostatic charging of the window material Sample Handling Challenge resulting in particles sticking to surfaces; Sample handling within CheMin is new and has never been flown before. The vibration of the sample cell is a tuning 4. Potential increase in the electrostatic field effects fork style arrangement, is localized and less coupled, and due to window oil-canning, i.e., windows flexing as the cell is vibrated; has the advantage of minimizing the ejection of material. It has solved the problem of how to remotely, randomly 5. Secondary charge transfer effects which may result arrange material within the instrument for XRD. in layering of particles;

Figure 9: Results of SNR progressive improvement

Figure 10: Left Image – Weathered regolith particles / Right Image – Angular Interlocking particles

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preliminary samples chosen for testing were basalt, arkose, testing and problem resolution. This delay proved kaolinite, hematite and satin spar. Conditions such as loose invaluable to allowing the instrument to reach flight sample left within the instrument and volume residual maturity. In closing, to date the CheMin instrument is material remaining in the cell after cleaning were only working well on Mars. The instrument received its first marginally tested in an attempt to lengthen the life of the regolith sample for analysis on October 18, 2012. Figure instrument. At the end of the day, one must accept that 13 shows the actual diffraction pattern resulting from that testing might be imperfect, but good enough to give a high first analysis. likelihood of success. ACKNOWLDGMENTS FPGA Schedule Challenge Many people have contributed to the success of the CheMin During the Integration and Test phase of the flight implementation and deserve to be acknowledged: instrument, it became clear that the final challenge was to finalize the FPGA firmware on schedule. Algorithms and Dr. David Vaniman (Co-I) sequences originally targeted for the FPGA were either removed or simplified. A test suite to validate the FPGA Thomas Glavich (JPL) was created. The problem was that early on in the project, major elements like the sample delivery/excitation issue, X- Dr. Albert Yen (Co-I, JPL) ray source delays, and thermal control dominated the Allen Farrington (JPL) instrument control system design and validation effort. These issues drove the schedule and placed a lot of pressure Soren Madsen (JPL) on the final S/W design and FPGA burn going into integration and test. Ultimately, the FPGA implementation Curtis Chen (JPL) was successful. Jennifer Dooley (JPL) 5. SUMMARY AND CONCLUSIONS J. Tse (JPL) It was a challenge transforming the legacy CheMin design used in the field to a flight instrument. Initially, the Dean Johnson (JPL) proposed completion cost was $15M, but the instrument project failed its preliminary design review (PDR), causing Jeffrey Srinivasan (JPL) a re-plan and capping the cost at almost 3x the initial estimate. Not appreciating the true technology readiness Pavani Peddada (JPL) level, vendor capability (i.e., the X-ray source), and the large array of sample excitation variables that needed to be Eric Olds/Mark Russel (Swales) tested made the flight implementation very challenging. The MSL CheMin instrument was originally scheduled for Robert Debusk (JPL) delivery to MSL rover integration in July 2008. However, David Muliere (JPL) with the delay of the MSL launch from 2009 to 2011, more time was given to the MSL CheMin Team for limited Mark Lysek (JPL)

Mellani Hunt/Christopher Brennen (CalTech)

The work described in this paper was performed at the Jet Propulsion Laboratory, California Institute of Technology under a contract with the National Aeronautics and Space Administration (NASA). Reference herein to any specific commercial product, process or service by trade name, trademark, manufacturer, or otherwise, does not constitute or imply its endorsement by the United States Government, NASA or the Jet Propulsion Laboratory, California Institute of Technology.

REFERENCES

[1] Mars Science Laboratory CheMin Experiment Figure 13: Mars Regolith Sample Implementation Plan, JPL D-22249, MSL-415-0437, January 30, 2008.

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[2] Mars Science Laboratory CheMin Functional infrared sensor data analysis and management software, Requirements Document, JPL D-27151, MSL-425- and MSL flight software code generation tools. Prior to 0439, January 28, 2008. coming to JPL, he worked on several U. S. Navy sensor systems at both the software and system level. His interests [3] CheMin Instrument, Critical Design Review, JPL, July include real-time image processing and digital signal 17-19, 2007. processing for scientific instrumentation, autonomy, data management technologies, as well as software and systems [4] “Field Studies of the Mars Analog Materials Using a modeling and development techniques. Reder earned a B.S. Portable XRD/XRF Instrument,” P. Sarrazin, et.al., in Electronic Engineering from California Polytechnic Lunar and Planetary Science, XXXIX, 2008. University at San Luis Obispo, and an M.S. in Electrical Engineering from the University of Southern California. [5] Blake, D., “The Development of the CheMin XRD/XRF: Reflections on Building a Spacecraft William Harris has been Instrument, IEEE, January 2012. associated with the design, assembly, and test of flight [6] “Instrument Performance Model & Validation: instruments since coming to JPL in Instrument Error Budget,” C. Chen, JPL, May 30, 2007. January of 1959. His work has included involvement in the [7] “CHEMIN Noise Go-Forward Plan/Results,” W. Sargent Program, Mariner series, Zimmerman, et.al., November 2, 2011. Ranger Series, Voyagers 1 and 2 (MDS), Microwave [8] “Investigation of the Effects of Low Gravity/Low Sounder Unit Series, UARS Microwave Limb Sounder, Mars Pressure on Dust Sample Excitation,” W. Observer (PMIRR), 14 Cassini (ISS), CloudSat, GALEX, Zimmerman, et.al., JPL, Director’s Research and and MarsScience Lab (CheMin). Development Fund (DRDF), Final Report, October David Blake (PI) received a B.S. in 2007. Biological Sciences from Stanford

University in 1973. After a stint in the US BIOGRAPHY Navy, he attended graduate school at the University of Michigan, where he Wayne Zimmerman is currently the Chief received a Ph.D. in Geology & Engineer for the Instruments and Science Mineralogy in 1983. He came to Ames Data Systems Division at JPL. His Research Center as a NRC postdoctoral current responsibilities include trouble fellow, and became a research scientist in the Exobiology shooting science instrument problems and Branch at Ames in 1989. He was the Exobiology Branch insuring instruments meet performance, Chief from 2000-2004. In nearly 25 years of research schedule, and cost requirements. He also at Ames, he has studied astrophysical ices, interplanetary chairs both instrument design reviews and design teams for dust, Mars meteorites, lunar soils and stratospheric soot. on-orbit and in-situ science instrument payloads for He received NASA’s Exceptional Scientific Achievement planetary, lunar, and Earth science missions. He was Medal in 1999 for his work on Astrophysical Ice Analogs. actively involved in sample handling/processing/delivery He is the inventor and Principal Investigator of the technology development and insertion into flight projects CheMin instrument on Mars Science Laboratory and has like the MSL CHEMIN X-ray diffraction instrument and the led or worked on numerous spacecraft instrument projects. Mars Scout UREY astrobiology instrument. He is the acting project element manager for CHEMIN. Wayne received his John Michael Morookian received his B.S. in Fluidics from Case Institute of Technology, B.S. in Electrical Engineering from the Cleveland Ohio, and his M.S. in Aerospace Systems University of Southern California (1991), Engineering from the University of Southern California. began working at JPL in 1990 as an Wayne has been at JPL for 35 years building robotic academic part-time employee and is instrument delivery/sampling systems for Mars as well as currently a Senior Engineer in the designing integrated instrument platforms for terrestrial Payloads and Observing Systems group and planetary applications. within the Systems Engineering section. He is the recipient of both a NOVA and a Technology and Leonard J. Reder returned to JPL in 1999, as a Real-Time Applications Programs Exceptional Service Award for Senior Software Engineer to work on the Keck achievement in the area of fiber-optic links. He has spent Interferometer Project. He contributed to software for high the last decade developing in situ instruments for planetary speed, closed-loop control of optical delay lines, created exploration, most notably the Microscopy Electrochemistry auto- alignment software, and developed a high-level Conductivity Analyzer (MECA) instrument for the Phoenix science sequencer implementation. He has developed mission and CheMin for the Mars Science Lab. machine learning applications, Mars surface simulation,

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